Caption: Adrenaline molecule. Computer graphic of the hormone adrenaline, or epinephrine (formula C9. H13. N.O3). The atoms (spheres) are colour- coded: carbon (yellow), oxygen (red), nitrogen (blue) & hydrogen (white). Adrenaline is a hormone produced in the adrenal glands above the kidneys. It is released at times of stress or fear to allow the body to work harder for a short time, leading to a "fight or flight" response. It increases the speed and force of the heartbeat, widens the airways to allow the lungs to take in more oxygen, and directs blood to the muscles to allow them to work harder. It is also used as a drug to treat severe asthma and anaphylactic shock.